Posted
by
timothyon Friday May 21, 2010 @08:01PM
from the we-can't-always-get-what-we-want dept.

FleaPlus writes "The Air Force is initiating a pathfinder program to develop a first-stage rocket booster capable of gliding back to a runway so it can be easily reused. Lockheed Martin has already launched a secretive prototype, and a Cal Poly team has a prototype based on Buzz Aldrin's Starcraft/StarBooster design (video). The Air Force estimates such a booster could cut launch costs by 50% over the current Atlas 5 and Delta 4 rockets, and could also offer a rapid surge/replacement capability if combined with reusable spacecraft like the recently launched X-37B. Initial test flights are planned for 2013."

1) You shouldn't reuse rockets. They are the most stressed components on Earth and space... They're just tubes full of fuel and some fiddly bits. The fiddly bits are not worth trying to reuse. I thought we learned that by now.2) OK, so the skin of the rocket, assuming it doesn't do double-duty as fuel tank, should split in 4 like a banana, and turn into a helicopter.

The current problem is that these rockets tend to shred themselves to pieces except for their fragile payload, and drop anything that is left into the ocean. This is considered by many to be a waste of an otherwise good rocket. Now, the feasibility and economics of repairing and reusing what is essentially a long tube filled with exploding fuel is a completely different story...

The Shuttle was a goat from the first test flight. The original design was for fully reusable components and all liquid fuel. Constant budget cuts and politics took a great idea and destroyed it.

Why solids? A Powerful Senator from Utah, where Morton-Thiokol is based. and NASA's director hailed from as well. Couple that with Congress and the White House back in the early 70's constantly cutting budgets. Solids are easier to design with, just more expensive to operate in a reusable configuration. An alternative solid design by another vendor (Aero-concepts I think) actually had the necessary tangs and O-rings to ensure there wouldn't be a Challenger style disaster - but they weren't based in Utah. As a matter of fact, their proposal was to ship them on barges due to proximity to Kennedy, minimizing the probability of warping - another constant problem caused by shipping the solids from Utah to Florida on train cars.

Why that big throw-away tank? Because a fly-back vehicle was abandoned due to design budget cuts by Congress. So now we have a throw-away tank and poorly designed solid rocket boosters on a system that was originally intended to have neither.

It wouldn't surprise me if Congress and the White House doesn't manage to repeat the same mistakes made almost 40 years ago.

Another idea of the "fly-back" booster is something that has already been done - launch a Pegasus from an actual jet. The Space Shuttle's boosters just used parachutes, I didn't see that addressed, I suppose maybe they didn't want salt water in a liquid fueled rocket engine. But it seems like wings are still an issue, those wings are huge, and I don't think they're light. It seems like too much expense that could drag down the real cost savings

Agreed, if I was NASA I probably would have kept sinking cash into the X-33 and X-37 projects although from a budget standpoint NASA also gets the short end of the stick. True, the X-33 had design challenges that would take a long time to be worked out but, to me SSTO spacecraft is the most logical next step after the shuttle.

I think it would be a mistake to assume that. An orbital ship isn't fundamentally any more complicated than a passenger jetliner. I expect something like SSTO or 2STO is probably doable with low operational overhead, and a working flyback booster gets us half way to 2STO. I'm a big proponent of SSTO myself, and would like to see DC-X (or something like it) restarted.

I think you gravely misunderstand and underestimate the rigors of rocketry. The stresses encountered are nothing at all like in your car or even a jet turbine. You're basically continually exploding gallons of fuel per second at very high temperatures and pressures. Right on the other side of the bell, you have turbopumps spinning at very high speeds and at cryogenic temperatures. Toss in the monstrous vibrations and stresses, sorry, you DON'T reuse the parts.

If a rocket flies succesfully, you know the design works, kind of. The engineering is at or beyond the bleeding edge. In the Apollo days there was a lot of fudging and kluging to get the F-1 to work, and the Space Shuttle is no better.

This is because this stuff is HARD. Materials don't get stronger or behave differently because they're in rockets. They're manufactured, designed and built by humans and are subject to the same limits as any other product,

Basically, you know the design works, you keep the design. And you build many many many rocket parts. You use those.

Sort of like Formula One motors. No one reuses them. Why not? No one cares. You build them. You use them, they wear out after 20 hours, and you build another one. Simpler, cheaper, better.

The new budget revives the NASA Institute for Advanced Concepts (NIAC), which is the part of NASA which previously studied [usra.edu] space elevators. The NIAC was one of the parts of NASA which was cancelled to fund Constellation. Also, there have been a few Centennial Challenges related to space elevators, like the tether challenge and the beam power challenge.

For typical missions the Shuttle doesn't need much cross-range capability: You just wait for the orbit closest to going right over the landing site and go down then. This happens twice per day.

How often it happens is a product of orbital inclination and orbital altitude, for a typical Shuttle mission it happens on average twice a day.

You could get away with little stubby wings like the X-15.

That's what the designers of the Shuttle thought too, way back at the start of the design process. Then they actually started doing mission analysis - and discovered how very wrong they were. It turned out that average of only twice a day could leave the crew stranded, unable to reach a safe landing site, for periods of up to eighteen hours. Not good in the event of a problem on orbit, and the only way to fix it was to add cross range capability (read: bigger wings). They also discovered that lack of cross range capability limited the choice of abort scenarios and limited the orbital inclinations the Shuttle could reach. All of this meant the wings started growing - big and fast.

Once they did the computation right it turns out that the shuttle would only have a couple hundred pounds of payload to polar orbit. No launching spy satellites for you! Oops!

Wrong. Shuttle capacity to polar orbit is notionally 28000 pounds. (Probably greater now with the reduced weight External Tank developed for ISS missions.)

So the military didn't end up using the shuttle (except for a couple equatorial shots testing some gear).

Wrong again. At least one military Shuttle mission went into a 61 degree orbit. Several launched classified satellites.